The four day sea trial was conducted aboard the United States Coast Guard Cutter MOBILE BAY (WTGB-103) for the purpose of assessing the seakeeping performance characteristics of this vessel class. Time correlated ship motion measurements as well as crew performance data were obtained. Trial results indicate that excessive wetness and rolling as well as substantial crew performance impairments will occur in even mild seas of 6-foot significant wave height. A simple method for collecting crew performance data was demonstrated. Results demonstrate the best speed/heading combinations and highlight ship locations where habitation may be a problem. Analytical predictions for the WTGB were made and compared to those of the 95-ft WPB Class cutter whose motion responses represent a known baseline of seakeeping qualities. Analytical results demonstrate that the 140-ft WTGB exhibits less ship motion than the 95-ft WPB except in roll, where sensitivity to natural roll period and the modal wave periods of the seaways become a factor. Predicted human performance data indicates a general superiority of the WTGB in all but quartering seas. An additional sea trial is recommended to compare directly the 140-ft WTGB and the 95-ft WPB in order to validate the analytical seasickness results presented herein.